1. Field of the Invention
This invention pertains to a temperature control device for satellite components and more particularly to a thermal switch for actively controlling heat flow rate between satellite components.
2. Description of Related Art
In many areas of technology, such as cryogenic refrigeration, spacecraft,and electronics, it is desirable to control the flow of heat from one area to another. In spacecraft, the traditional approach to temperature control for spacecraft component packages consists of mounting components with low interface resistances to "heat-sinking" decks and radiators. Severe requirements of maintaining narrow component package temperature ranges under wide variations of internal dissipation and external environment dictate requirements for decks and radiators which translate to the thermal design of the
Although this approach has been used for decades, passive temperature control of a typical spacecraft is inherently handicapped by variations of environmental fluxes and internal dissipation, surface optical properties, and uncertainties of flight temperature prediction, often equivalent to temperature variations on the order of 40.degree. C. With simple passive thermal control not satisfying requirements, semi-active (thermostats and heaters), or active (VCHP, CPL, louvers) control devices must often be employed, possibly accompanied by increased cost, weight, power, and testing complexity.
Removal of heat from heat-generating equipment on satellites and other spacecraft has been accomplished previously by various forms of heat pipes, phase-change medium, flexible heat conductors, such as a heat strap and reflectors in various combinations and in conjunction with other components. These devices convey heat to unique forms of heat exchangers, such as in Basilius, U.S. Pat. No. 4,673,030, where a heat tube in a tube in combination with a heat-exchange plate is taught; and in Hewitt, U.S. Pat. No. 4,420,035, arcuate radiator panels in conjunction with heat tubes in a circular spinning satellite are taught.
Heat switching devices with paraffin actuators, actuators based on the expansion of water as it freezes, and bi-material actuators based on two materials with large differences in coefficients of thermal expansion have been utilized. Paraffin actuators, while accepted state-of-the-art satellite hardware, are of high volume, mass, complexity, and high cost. Water-ice actuators, although they show future promise for high-force and reliable actuation, function only in the -5.degree. to 0.degree. C. range. Bi-material actuators are very large have too much thermal conductivity in the "off" mode.
While each prior art device has some advantage, none will automatically control the temperature of a package attached to a mounting platform serving as a heat sink at a low weight and cost.